1. Field of Invention
The present invention relates generally to methods for chemical vapor deposition (CVD) of silicon dioxide, and more particularly to a method for CVD of silicon dioxide at a high deposition rate and low reaction chamber pressure using a reactant gas including silane and oxygen.
2 . Description of the Prior Art
Silicon dioxide is one of the most commonly used materials in the manufacturing of semiconductor devices, and can be "grown" or "deposited" onto silicon substrates. Silicon dioxide is grown by subjecting the silicon substrate to oxygen or water vapor at high temperature, i.e. &gt;900.degree. C. (as documented in S. Wolf and R. N. Tauber, Silicon Processing for the VLSI Era, Volume 1 Process Technology, Lattice Press (1986), pages 198, 210). Deposited silicon dioxide is typically done by Chemical Vapor Deposition (CVD) at lower temperatures, i.e. .degree.600.degree. C. (See A. Sherman, Chemical Vapor Deposition for Microelectronics, Noyes Publications, Park Ridge, N.J. (1987), pages 66-77.)
Deposited oxides, because of the low temperature process, are used extensively as the insulating layer between multilayer metallization of today's integrated circuits. Silicon dioxide has been deposited by PVD (as disclosed in U.S. Pat. No. 4,624,859) and various CVD processes, both at atmospheric pressure (see U.S. Pat. No. 5,360,646) and at low pressures (see Sherman, pages 66-77). Low-pressure depositions have superior film qualities over depositions at atmospheric pressure and are therefore usually the process of choice (see Sherman, pages 66-77). Low pressure depositions are accomplished by placing a substrate in a vacuum chamber, heating the substrate and introducing silane (as disclosed in U.S. Pat. No. 4,900,591), or any similar silicon precursor such as dichlorosilane, silicon tetrachloride, TEOS (see U.S. Pat. No. 3,934,060) and the like, with oxygen or any similar oxygen precursor, e.g. nitrous oxide, ozone (see U.S. Pat. No. 5,000,113), etc. Deposition rates of approximately 20 to 30 angstroms per minute are typical for low pressure processes (&lt;1 Torr) (see Sherman, page 70), and 50 to 140 angstroms per minute are typical for high pressure processes (&gt;1 Torr) (see U.S. Pat. No. 4,900,591). Higher deposition rates of 2,000 angstroms per minute have been reported for plasma enhanced depositions (see U.S. Pat. No. 5,000,113). Although all of these CVD processes have been used in manufacturing of microelectronics, they all have disadvantages. For example, the process may have a very low rate of deposition, or poor uniformity across the silicon substrate, or high tensile stress (see Sherman, pages 68-77), or the process may incorporate unwanted by-products such as moisture, which degrades the film properties.
U.S. Pat. No. 5,551,985 by Brors et al. describes a CVD reactor that provides improved uniformity in heating a wafer, and a highly uniform gas flow across the surface of a wafer. U.S. Patent. No. applications Ser. Nos. 08/909,461 filed on Aug. 11, 1997, and 09/228,835 and 09/228,840 filed on Jan. 12,1999, the disclosures of which are incorporated herein by reference, describe wafer chambers in which related processes may also be used.